Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/004—Photosensitive materials
  • G03F7/09—Photosensitive materials characterised by structural details, e.g. supports, auxiliary layers
  • G03F7/095—Photosensitive materials characterised by structural details, e.g. supports, auxiliary layers having more than one photosensitive layer
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/004—Photosensitive materials
  • G03F7/075—Silicon-containing compounds
  • G03F7/0757—Macromolecular compounds containing Si-O, Si-C or Si-N bonds
  • G03F7/0758—Macromolecular compounds containing Si-O, Si-C or Si-N bonds with silicon- containing groups in the side chains
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/004—Photosensitive materials
  • G03F7/09—Photosensitive materials characterised by structural details, e.g. supports, auxiliary layers
  • G03F7/094—Multilayer resist systems, e.g. planarising layers
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/004—Photosensitive materials
  • G03F7/0045—Photosensitive materials with organic non-macromolecular light-sensitive compounds not otherwise provided for, e.g. dissolution inhibitors
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S430/00—Radiation imagery chemistry: process, composition, or product thereof
  • Y10S430/1053—Imaging affecting physical property or radiation sensitive material, or producing nonplanar or printing surface - process, composition, or product: radiation sensitive composition or product or process of making binder containing
  • Y10S430/1055—Radiation sensitive composition or product or process of making
  • Y10S430/106—Binder containing
  • Y10S430/111—Polymer of unsaturated acid or ester

Definitions

• This invention relates to a resist material, and a pattern forming process using the resist material.
• a technology called "two-layered resist process” which comprises the steps of forming a lower resist layer for levelling on a to-be-patterned material (to-be-etched material), then forming an upper resist layer, exposing this upper resist layer, developing, and transferring the resulting pattern to the lower resist layer to obtain a mask pattern.
• a resist material for constituting the upper resist layer must have performance capable of withstanding at least etching for transferring the pattern to the lower resist layer (generally O2 RIE, that is, reactive ion etching using oxygen).
• Polyacrylate type resists, polysiloxane type resists and polysilane type resists have high etching resistance due to the introduction of silicon (Si) into an ester portion of the resist materials. They are known as the materials for the upper layer resist material in the multi-layer resist process described above (for example, Japanese Unexamined Patent Publication (Kokai) Nos. 2-191957, 2-239251, 3-217845, 3-261952 and 4-42229). In all of them, development is based on the difference of molecular weights between exposed area at the time and unexposed area. As a result, sharp patterning cannot be conducted and swell of the resist pattern occurs at the time of development, limiting their usefulness for obtaining miniature patterns. Because of the ever-increasing integration density of semiconductor devices, this is a significant drawback.
• the present invention provides a resist material comprising a copolymer represented by the following general formula I and a photo-acid generator: wherein each of R1 and R3 independently represents a hydrogen, alkyl having 1 to 4 carbon atoms, halogen, halogenated (C1 - C4) alkyl, nitrile or phenyl, R2 is a group represented by the following general formula II, wherein R5 is a C1 - C4 alkylene, each of R6, R7 and R8 independently represents a C1 - C4 alkyl, halogenated (C1 - C4) alkyl, phenyl or tri(C1 - C4)alkylsilyl(C1 - C4) alkyl; R4 is a group which is eliminated by an acid, and each of m and n is a positive integer.
• typical examples of the group R4 eliminated by the acid are t-butyl, dimethylbenzyl, tetrahydropyranyl and 3-oxocyclohexyl.
• the photo-acid generator useful for the present invention may include sulfonium salts, sulfonic acid ester compounds, iodonium salts and halogen compounds.
• Typical examples of the photo-acid generator include the following compounds: sulfonium salts of the formula, in which X ⁇ is BF4 ⁇ , PF6 ⁇ , SbF6 ⁇ or CF3SO3 ⁇ , and R is -H, -OCH3 or sulfonic acid ester compounds of the formulae, in which R is in which R1 is -H or -CH3, and R2 is -C4H9, or iodonium salts of the formula, in which X ⁇ is BF4 ⁇ , PF6 ⁇ , SbF6 ⁇ or CF3SO3 ⁇ , and R1 and R2 are each independently -H, -OCH3 or -C(CH3); and halogen compounds of the formulae, in which X is -Br or -Cl, in which R is
• a pattern forming process which comprises the steps of coating the resist material described above on a substrate to form a resist layer, irradiating the resist layer, baking the irradiated resist layer, and developing the baked resist layer.
• the resist material according to the present invention contains a copolymer of a silicon (Si)-containing acrylate and an acrylate which contains a group eliminated by an acid (protonic acid), the polarity of which changes after elimination of this group, and which then becomes soluble in an aqueous alkali solution (developing solution), as a base polymer. Further, this resist material contains a photo-acid generator which generates a protonic acid upon irradiation, which acts on the base polymer and generates conversion of the polarity, making the resist material becomes soluble in the aqueous alkali developing solution (or a solution prepared by further adding C1 to C8 alcohol to the former).
• the resist material is not completely insoluble in the developing solution which is usually an organic solvent, even at the portion having a large molecular weight, but slightly dissolves or swells. For this reason, it is not possible to generate a large difference in developability between the exposed area and the unexposed area.
• the resist material according to the present invention in contrast, development is effected on the basis of the difference of polarities between the exposed region and the unexposed regions, so that a clear difference occurs between the area soluble in the developing solution and the area insoluble in it. Further, according to the present invention, further, the region in which polarity conversion occurs can be developed by the aqueous alkali developing solution which does not cause swelling. Consequently, degradation of the exposed pattern can be restricted.
• the resist material of the present invention described above is clearly suited for use as an upper resist layer of a multi-layered resist process.
• the lower layer resist pattern is formed by the steps of coating the resist material described above on the lower resist layer, which is in advance formed on the substrate, to form the upper resist layer, irradiating this upper resist layer, effecting baking and development so as to form a pattern of the upper layer resist, and then forming the lower layer resist pattern using this upper layer resist pattern as a mask. Formation of this lower layer resist pattern can be carried out by ordinary O2 RIE (reactive ion etching using oxygen), by way of example.
• O2 RIE reactive ion etching using oxygen
• the present invention provides a pattern forming process which comprises forming an upper layer resist pattern by the process already described, irradiating the upper layer resist, effecting baking and then etching the lower layer resist. The irradiation by flood exposure not using a mask and heat-treatment may be conducted only for the upper layer resist pattern portion.
• the resist material according to the present invention has extremely high resolution, and is therefore suitable for ultra-miniature etching, in particular.
• this material is used as the upper layer resist of the multi-layered resist, there occurs the problem that a sufficient effect can be obtained only when the film thickness of the lower layer resist as the to-be-etched material is small, such as below 1.5 ⁇ m.
• a side etching degree corresponding to the upper layer resist pattern becomes much even when etching is effected by an anisotropic etching apparatus, and the line width of the upper layer resist pattern itself becomes slender, so that the line width of the resulting lower layer resist becomes slender.
• this problem can be solved by irradiating the upper resist layer after the upper layer resist pattern is formed, then effecting baking, subsequently etching the lower layer resist, and forming the pattern. It is believed that since the radiation exposed the residual resist layer remaining as the upper layer resist pattern after patterning of the upper layer resist but before etching of the lower layer resist and then baking is conducted, the group which is eliminated by the acid is eliminated from the copolymer in this upper layer resist and as a result, the Si content remaining in the resist layer becomes relatively greater and etching resistance of this resist layer can be improved.
• the present invention further provides a process for peeling the layer made of the resist material containing the Si-containing polymer and a photo-acid generator, which comprises the steps of irradiating a layer of this resist material effecting baking and then subjecting the resist to a peeling step.
• the Si-containing resist has resistance to oxygen plasma etching.
• the Si-containing resist is used particularly as the upper layer resist in a two-layered resist process, for forming a mask for etching the lower layer resist not containing Si.
• peeling of the resist not containing Si is conducted by ashing by oxygen plasma.
• peeling by a mixed gas of oxygen and CF4 or CHF3 has been proposed in the past, but this is not perfect.
• the substrate to be etched is PSG or a thermal oxide film, for example, a mixture of O2, CF4 and CHF3 is used as the etching gas.
• the upper layer resist and the substrate are etched simultaneously, but the etching of the upper layer resist is also not perfect. Therefore, a resist residue is formed from the upper layer resist.
• the Si-containing resist is rendered soluble by the function of the acid from the photo-acid generator at the exposed area and is removed and the pattern is formed by the resist at the unexposed area
• the resist remaining as the pattern is rendered soluble by the function of the acid from the photo-acid generator when the treatment is carried out, after etching of the lower layer resist, in accordance with the present invention as described above, and consequently, peeling can be accomplished by the developing solution.
• the resist can be removed and the pattern is formed by the resist at the unexposed area, Si in the resist remaining as the pattern is eliminated from the resist when treatment is carried out in accordance with the present invention as described above, Si in the resist is eliminated from the resist remaining as the pattern and resistance to the O2 plasma is lost. Accordingly peeling can be accomplished by ashing in the same way as in the case of the ordinary resist.
• the upper layer resist too, is simultaneously peeled by this etching step for the lower layer resist without the peeling step of the upper layer resist, in particular.
• flood exposure by radiation and heat-treatment are preferably applied to the entire surface of the resist layer inclusive of the upper and lower resist layers forming the pattern, and the irradiation and baking may be carried out simultaneously.
• TMSMMA Trimethylsilylmethyl methacrylate
• DBMA dimethylbenzyl methacrylate
• AIBN 2,2'-azobis(isobutylonitrile)
• TPSSbF6 triphenylsulfonium hexafluoroantimonate
• MIBK methyl isobutyl ketone
• TMSMMA Trimethylsilylmethyl methacrylate
• TBMA tertiarybutyl methacrylate
• TMSMMA Trimethylsilylmethyl methacrylate
• TPMA tetrahydropyranyl methacrylate
• the resist material of this example was obtained in the same way as in Example 1 using the base polymer described above.
• 1-methacryloxymethyl-1,1,3,3,3-pentamethyldisilylmethylene and dimethylbenzyl methacrylate were mixed at a mixing ratio of 1:1 so as to form a toluene solution having a monomer concentration of 5 mol/liter.
• 2 mol%, on the basis of the monomer, of AIBN was added to the mixture, and the mixture was retained in an oil bath at 80°C for 8 hours with stirring. Then, the mixture was left standing at room temperature to cool, and the reaction product was diluted with toluene.
• the toluene solution was dropped into large quantities of a mixed solvent of water and methanol having a mixing ratio of 1:20, and the resulting precipitate was filtered and dried to obtain a 1-methacryloxymethyl-1,1,3,3,3-pentamethyldisilylbenzylmethylene/dimethylbenzyl methacrylate copolymer represented by the following formula, at a yield of 65%.
• the molecular weight was 14,000 and the dispersion was 1.65. wherein each of m and n is a positive integer.
• the resist material of this example was obtained in the same way as in Example 1 using the base polymer described above.
• Diphenylmethylsilyl methacrylate and dimethylbenzyl methacrylate were mixed at a mixing ratio of 1:1 so as to form a toluene solution having a monomer concentration of 5 mol/liter.
• 2 mol%, on the basis of the monomer, of AIBN was added to the mixture, and the mixture was retained in an oil bath at 80°C for 8 hours with stirring. Then, the mixture was left standing at room temperature to cool, and the reaction product was diluted with toluene.
• the toluene solution was dropped into large quantities of methanol, and the resulting precipitate was filtered and then dried to obtain a diphenylmethylsilyl methacrylate/dimethylbenzyl methacrylate copolymer represented by the following formula, at a yield of 88%.
• the molecular weight was 20,000 and the dispersion was 1.74. wherein each of m and n is a positive integer.
• the resist material of this example was obtained in the same way as in Example 1 using the base polymer described above.
• 3-oxocyclohexyl methacrylate and trimethylsilylmethyl methacrylate were mixed at a mixing ratio of 1:1 so as to form a toluene solution having a monomer concentration of 5 mol/liter.
• 2 mol%, on the basis of the monomer, of AIBN was added to the mixture, and the mixture was retained in an oil bath at 80°C for 5 hours with stirring. Thereafter, the mixture was left standing at room temperature to cool, and the reaction product was diluted with toluene.
• the toluene solution was dropped into large quantities of a mixed solvent of methanol and water having a mixing ratio of 20:1, and the resulting precipitate was filtered and dried to obtain a trimethylsilylmethyl methacrylate/3-oxocyclohexyl methacrylate copolymer represented by the following formula, at a yield of 57%.
• the molecular weight was 13,000 and the dispersion was 1.81. wherein each of m and n is a positive integer.
• the resist material of this example was obtained in the same way as in Example 1 using the base polymer described above.
• t-butyl methacrylate and trimethylsilylmethyl acrylate were mixed at a mixing ratio of 1:1 so as to form a toluene solution having a monomer concentration of 5 mol/liter.
• 2 mol%, on the basis of the monomer, of AIBN was added to the mixture, and the mixture was retained in an oil bath at 80°C for 3 hours with stirring. Thereafter, the mixture was left standing at room temperature to cool, and the reaction product was diluted with toluene.
• the toluene solution was dropped into large quantities of a mixed solvent of methanol and water having a mixing ratio of 1:1, and the resulting precipitate was filtered and dried to obtain a trimethylsilylmethyl acrylate/t-butyl methacrylate copolymer represented by the following formula, at a yield of 85%.
• the molecular weight was 23,000 and the dispersion was 1.63. wherein each of m and n is a positive integer.
• the resist material of this example was obtained in the same way as in Example 1 using the base polymer described above.
• the substrate was hard baked at 200°C so as to form a lower layer resist layer having a thickness of 1.5 ⁇ m.
• This lower layer resist layer had a function of levelling the unevenness on the substrate.
• the resist material obtained in each of Examples 1 to 7 was applied to the surface of the lower resist layer and was then baked at 60°C to form a 0.3 ⁇ m-thick upper resist layer.
• each of the resist materials was developed by an alkali developing solution (NMD3, a product of Tokyo Oka Kogyo K.K.) or a solution prepared by adding isopropyl alcohol (IPA) or isobutyl alcohol (IBA) to the alkali developing solution, for one minute so as to pattern the upper resist layer. According to each resist material, a pattern corresponding to a line-and-space of 0.3 ⁇ m could be sufficiently resolved.
• NMD3 alkali developing solution
• IPA isopropyl alcohol
• IBA isobutyl alcohol
• the lower resist layer was etched by using the pattern of the upper layer resist layer as a mask.
• Oxygen etching (O2 RIE) using a reactive ion etching apparatus of a parallel plate type was suitable for this etching.
• the pattern of the upper resist layer could be transferred with fidelity to the lower resist layer.
• this resist was spin-coated onto a novolak type resist (film thickness: 2.0 ⁇ m) which was hard baked at 200°C for one hour, and was pre-baked at 60°C for 100 seconds (film thickness: 3,500 ⁇ ).
• NMD-3 aqueous alkali developing solution
• Example 9 The same procedures of Example 9 were followed except that irradiation of the entire surface after development and the baking step were omitted.
• etching of the 2.0 ⁇ m-thick lower layer was completed, the residual film of the upper layer resist hardly existed, so that the pattern became slender, and a shift was severe.
• a novolak resist was coated onto a substrate consisting of PSG and was baked at 200°C for 1 hour to form a lower resist layer.
• a Si-containing resist consisting of a trimethylsilylmethyl methacrylate/a dimethylbenzyl methacrylate copolymer and triphenylsulfonium hexafluoroantimonate as a photo-acid generator was coated and was then baked at 60°C for 100 seconds so as to form a 0.3 ⁇ m-thick upper resist layer.
• the upper resist layer was developed for one minute by an aqueous alkali developing solution (NMD-3, a product of Tokyo Oka Kogyo K.K.) and an upper layer resist pattern was obtained.
• NMD-3 aqueous alkali developing solution
• the lower layer resist was etched by O2 RIE, and a two-layered resist pattern was formed.
• the laser beam was irradiated again on the entire surface by the same KrF excimer laser stepper, and baking was again carried out at 60°C for 60 seconds.
• the upper layer resist could be peeled.
• a novolak resist was coated onto a substrate consisting of PSG and was baked at 200°C for one hour to form a lower layer resist layer having a thickness of 1.5 ⁇ m.
• a Si-containing resist consisting of a trimethylsilylmethyl methacrylate/t-butyl methacrylate copolymer and triphenylsulfonium hexafluoroantimonate as a photo-acid generator was coated and was then baked at 60°C for 100 seconds so as to form an upper resist layer having a thickness of 0.3 ⁇ m.
• the upper resist layer was developed for one minute by an aqueous alkali developing solution (NMD-3, a product of Tokyo Oka Kogyo K.K.) and an upper layer resist pattern was obtained.
• NMD-3 aqueous alkali developing solution
• the lower layer resist was etched by O2 RIE, and a two-layered resist pattern was formed.
• the laser beam again irradiated the entire surface, using the same KrF excimer laser stepper, and baking was again carried out at 100°C for 60 seconds.
• the upper layer resist could be peeled.
• a novolak resist was coated onto a substrate consisting of PSG and was baked at 200°C for one hour to form a lower layer resist layer having a thickness of 1.5 ⁇ m.
• a Si-containing resist consisting of a trimethylsilymethyl methacrylate/tetrahydropyranyl methacrylate copolymer and triphenylsulfonium hexafluoroantimonate as a photo-acid generator was coated and was baked at 60°C for 100 seconds so as to form an upper resist layer having a thickness of 0.3 ⁇ m.
• the upper resist layer was developed for one minute by an aqueous alkali developing solution (NMD-3, a product of Tokyo Oka Kogyo K.K.) and a upper layer resist pattern was obtained.
• NMD-3 aqueous alkali developing solution
• the lower layer resist was etched by O2 RIE, and a two-layered resist pattern was formed.
• the laser beam again irradiated the entire surface, using the same KrF excimer laser stepper, and baking was again carried out at 60°C for 60 seconds.
• the upper layer resist could be peeled.
• a novolak resist was coated onto a substrate consisting of PSG and was baked at 200°C for one hour to form a lower resist layer having a thickness of 1.5 ⁇ m.
• a Si-containing resist consisting of polydimethylisopropylsilyl maleimide expressed by the formula given below and triphenylsulfonium hexafluoroantimonate as a photo-acid generator was coated on the lower resist layer, and was baked at 90°C for 100 seconds to form an upper layer resist layer having a thickness of 0.3 ⁇ m: wherein n is a positive integer.
• the upper resist layer was developed for one minute by an aqueous alkali developing solution (NMD-3, a product of Tokyo Oka Kogyo K.K.), and an upper layer resist pattern was obtained.
• NMD-3 aqueous alkali developing solution
• the lower resist was etched by O2 RIE, and a two-layered resist pattern was formed.
• the laser beam again irradiated the entire surface using the same KrF excimer laser stepper, and baking was again carried out at 100°C for 60 seconds.
• the upper layer resist could be peeled.
• a novolak resist was coated onto a substrate consisting of PSG, and was baked at 200°C for one hour to form a lower resist layer having a thickness of 1.5 ⁇ m.
• a Si-containing resist consisting of silylated polyhydroxystyrene expressed by the formula given below and triphenylsulfonium hexafluoroantimonate as a photo-acid generator was coated onto this lower resist layer, and was baked at 90°C for 100 seconds to form an upper resist layer having a thickness of 0.3 ⁇ m: wherein each of m and n is a positive integer.
• this upper resist layer was developed by an aqueous alkali developing solution (NMD-3, a product of Tokyo Oka Kogyo K.K.) for one minute, and an upper layer resist pattern was obtained.
• NMD-3 aqueous alkali developing solution
• the lower layer resist was etched by O2 RIE, and a two-layered resist pattern was obtained.
• the laser beam again irradiated the entire surface by the same KrF excimer laser stepper, and baking was again carried out at 100°C for 60 seconds.
• the upper resist layer could be peeled.
• Example 16 In the procedures of Example 16 described above, ashing was carried out after etching of PSG without exposing the entire surface after O2 RIE and the subsequent baking operation. As a result, a resist residue was formed, and ashing could not be carried out sufficiently.
• the present invention provides a resist material which has high resolution and which can be developed by an aqueous alkali developing solution. Accordingly, the resist material can satisfy the requirements for miniature patterns in the semiconductor industry. Further, a thick lower layer resist can be etched by using a chemical amplification type resist consisting of a Si-containing methacrylate resin having high resolution and a photo-acid generator, and a pattern having a high aspect ratio can be obtained. The Si-containing resist can be peeled by a simple treatment.

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• 1993
  • 1993-12-27 JP JP5331746A patent/JP2980149B2/ja not_active Expired - Lifetime
• 1994
  • 1994-06-27 DE DE69405955T patent/DE69405955T2/de not_active Expired - Lifetime
  • 1994-06-27 EP EP94304637A patent/EP0645679B1/fr not_active Expired - Lifetime
• 1996
  • 1996-03-18 US US08/618,274 patent/US5856071A/en not_active Expired - Lifetime

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